Disposable diapers

ABSTRACT

Disposable absorbent diapers are provided with improved comfort, fit and liquid transportation. The absorbent core of the disposable absorbent diapers includes at least one absorbent structure having a substrate layer and an absorbent layer with channels.

FIELD

The present disclosure relates to disposable diapers providing animproved fit in dry and wet states (i.e., when loaded with bodilyfluids) and providing improved liquid transportation.

BACKGROUND

Disposable absorbent articles for receiving and retaining bodilydischarges such as urine or feces are generally known in the art.Examples of these include disposable diapers, training pants and adultincontinence articles. Typically, disposable diapers comprise a liquidpervious topsheet that faces the wearer's body, a liquid imperviousbacksheet that faces the wearer's clothing and an absorbent coreinterposed between the liquid pervious topsheet and the backsheet.

Since their introduction into the market place, disposable diapers havecontinued to improve regarding comfort, fit and functionalities.

An important component of disposable absorbent articles is the absorbentcore structure. The absorbent core structure typically includesabsorbent polymer material, such as hydrogel-forming polymer material,also referred to as absorbent gelling material, AGM, or super-absorbentpolymer, SAP. This absorbent polymer material ensures that large amountsof bodily fluids, e.g. urine, can be absorbed by the absorbent articleduring its use and be locked away, thus providing low rewet and goodskin dryness.

Traditionally, the absorbent polymer material is incorporated into theabsorbent core structure with cellulose or cellulosic fibres. However,over the past years, significant effort has been spent to make thinnerabsorbent core structures which can still acquire and store largequantities of discharged body fluids, in particular urine. Hereto, ithas been proposed to reduce or eliminate these cellulose fibres from theabsorbent core structures. To maintain the mechanical stability of theabsorbent core structures, small quantities of thermoplastic adhesivematerial, such as fibrous thermoplastic adhesive material, may be addedto stabilize the absorbent polymer material. Resultantly, absorbentstructures having the required permeability/porosity, reducedgel-blocking, and that form stable structures in use or transport areprovided.

However, it was found that some absorbent core structures with reducedcellulose fibre content, whilst being very thin when not loaded withbodily fluids, may have an increased stiffness when partially loaded orfully loaded, especially in those regions which comprise most of theabsorbent capacity of the absorbent article, such as the front regionand crotch region of the diaper. Increased stiffness is not desirablesince it reduces the absorbent article's ability to conform to the bodyof the wearer once worn. Furthermore, it was also found that someabsorbent core structures which comprise absorbent polymer particles ofhigh absorption capacity swell significantly upon loading with bodyexudates. As a result, the volume of the absorbent article may increasesignificantly during use, especially in these regions which comprisemost of the absorbent capacity of the absorbent article, such as thefront region and crotch region of the diaper. Such an increase in volumemay render the disposable article uncomfortable for the wearer. It wasalso found that some of these absorbent core structures with reducedcellulose fibres content may have a reduced void volume which impactsnegatively the liquid acquisition speed.

Therefore there is still a need for disposable diapers having goodliquid handling properties and having an increased flexibility duringthe whole use of the article and which deliver, in particular, a betterfit in the wet state.

SUMMARY

The present disclosure generally relates to a disposable diaper having atransverse and longitudinal dimension. The disposable diaper comprises abacksheet, a topsheet and an absorbent core disposed therebetween. Theabsorbent core comprises at least one absorbent structure comprising asubstrate layer and an absorbent layer. The absorbent layer comprisesabsorbent polymer particles, and optionally cellulose fibers, supportedby and immobilized on the substrate layer. The absorbent layer has atransverse and longitudinal dimension and a thickness, a pair ofopposing longitudinal edges extending in the longitudinal dimension, apair of opposing transversal edges extending in its transverse dimensionand a front, crotch and back regions arranged sequentially in thelongitudinal dimension. The central longitudinal axis of the absorbentlayer delimits two longitudinal portions. The absorbent layer maycomprise one or more main channels substantially free of said absorbentpolymer particles extending through its thickness and at least presentin the crotch region; and one or more secondary channels substantiallyfree of the absorbent material extending through the thickness of theabsorbent layer. The secondary channels may be shorter than the mainchannels. In other embodiments, at least two main channels are separatedby a first minimum transverse spacing and at least two secondarychannels are separated by a second minimum transverse spacing, whereinthe first minimum transverse spacing is different than the secondminimum transverse spacing.

In certain embodiments, the absorbent layer does not comprise channelssubstantially free of absorbent polymer particles extending up to itslongitudinal and transverse edges.

Further, each channel may comprise a width of at least 3 mm or of atleast 4% of the transverse dimension of the absorbent layer, and/orextend over at least 15% of the longitudinal dimension of the absorbentlayer. The channels may be at least present in the crotch region or partthereof. In some nonlimiting examples, the absorbent layer may notcomprise channels substantially free of absorbent polymer particlesextending in its transverse dimension in the crotch region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a disposable diaper in accordance with onenon-limiting embodiment.

FIG. 2 is a perspective view of an absorbent structure comprising anabsorbent layer with two longitudinal main channels in accordance withone non-limiting embodiment.

FIG. 3A is a perspective view of an absorbent layer comprising fourlongitudinal main channels in accordance with one non-limitingembodiment.

FIG. 3B is a top view of an absorbent structure comprising an absorbentlayer with four longitudinal main channels in accordance with onenon-limiting embodiment.

FIG. 3C is a perspective view of the absorbent structure of FIG. 3B inaccordance with one non-limiting embodiment.

FIGS. 4A to 4E are schematic representations of channels in accordancewith various non-limiting embodiments.

FIG. 5 is a perspective view of an absorbent layer comprising twolongitudinal main channels at least present in the crotch region and twolongitudinal secondary channels in the front region in accordance withone non-limiting embodiment.

FIG. 6 is a perspective view of an absorbent layer comprising twolongitudinal main channels at least present in the crotch region, twolongitudinal secondary channels in the front region and two longitudinalsecondary channels in back front region in accordance with onenon-limiting embodiment.

FIGS. 7 to 13 are schematic cross-sections of an absorbent core taken inthe transverse dimension in accordance with various non-limitingembodiments.

FIG. 14 is a schematic representation of a process for making anabsorbent structure comprising an absorbent layer with channels inaccordance with one non-limiting embodiment.

DETAILED DESCRIPTION Definitions

As used herein “diapers” refers to devices which are intended to beplaced against the skin of a wearer to absorb and contain the variousexudates discharged from the body. Diapers are generally worn by infantsand incontinent persons about the lower torso so as to encircle thewaist and legs of the wearer. Examples of diapers include infant oradult diapers and pant-like diapers such as training pants.

“Training pant”, as used herein, refers to disposable garments having awaist opening and leg openings designed for infant or adult wearers. Apant may be placed in position on the wearer by inserting the wearer'slegs into the leg openings and sliding the pant into position about awearer's lower torso. A pant may be preformed by any suitable techniqueincluding, but not limited to, joining together portions of the articleusing refastenable and/or non-refastenable bonds (e.g., seam, weld,adhesive, cohesive bond, fastener, etc.). A pant may be preformedanywhere along the circumference of the article (e.g., side fastened,front waist fastened).

“Disposable” is used herein to describe articles that are generally notintended to be laundered or otherwise restored or reused (i.e., they areintended to be discarded after a single use and, may be recycled,composted or otherwise disposed of in an environmentally compatiblemanner).

As used herein “absorbent structure” refers to a three dimensionalstructure useful to absorb and contain liquids, such as urine. Theabsorbent structure may be the absorbent core of an absorbent article ormay be part of the absorbent core of an absorbent article, i.e. anabsorbent component of the absorbent core, as will be further describedherein.

As used herein “absorbent core” refers to a component of an absorbentarticle typically disposed between a topsheet and backsheet of anabsorbent article. The absorbent core of an absorbent article maycomprise one or more absorbent structures and optionally further layers,such as for instance a cover layer.

“Absorbent polymer particles” as used herein refers to substantiallywater-insoluble polymer particles that can absorb at least 10 timestheir weight of a 0.9% saline solution in de-mineralized water asmeasured using the Centrifuge Retention Capacity test (Edana 441.2-01).

“Nonwoven material” as used herein refers to a manufactured web ofdirectionally or randomly orientated fibers, excluding paper andproducts which are woven, knitted, tufted, stitch-bonded incorporatingbinding yarns or filaments, or felted by wet-milling, whether or notadditionally needled. Nonwoven materials and processes for making themare known in the art. Generally, processes for making nonwoven materialscomprise laying fibers onto a forming surface, which may comprisespunlaying, meltblowing, carding, airlaying, wetlaying, coform andcombinations thereof. The fibers may be of natural or man-made originand may be staple fibers or continuous filaments or be formed in situ.

The term “basis weight” as used herein refers to the mass of a materialper unit area, i.e. the mass of absorbent polymer particles per unitarea, e.g. gram per square meter (gsm).

“Hot melt adhesive” as used herein refers to adhesives in alignment withthe description given in “Adhesion and Adhesives Technology: AnIntroduction” by Alphonsus V. Pocius (Hanser publishers Munich, 1997).Therein a hot melt is defined as an adhesive applied from the melt andgaining strength upon solidification.

In the following description of the present disclosure, the surface ofthe disposable diaper, or of an element thereof, which faces in use inthe direction of the wearer, is called the “wearer-facing surface”.Conversely, the surface facing in use in the direction of the garment iscalled the “garment-facing surface”. The disposable diaper, as well asany element thereof, such as, for example the absorbent structure, hastherefore a wearer-facing surface and a garment-facing surface.

Unless specified otherwise, the longitudinal dimension or length of anabsorbent layer as used herein is to be understood as the averagelength.

Unless specified otherwise, the transverse dimension or width of anabsorbent layer as used herein is to be understood as the average width.

Disposable Diapers

The disposable diaper 1, such as illustrated in FIG. 1, has alongitudinal dimension (along a longitudinal axis A) and a transversedimension (along a transverse axis B) perpendicular thereto.

One end portion of the diaper is configured as a front waist region 2(which is the front one third of the article, having one third of thelength of the article). The opposite end portion is configured as a backwaist region 3 (which is the back one third of the article, having onethird of the length of the article). An intermediate portion of thediaper is configured as a crotch region 4 (which is the centre one thirdof the article). The crotch region extends longitudinally between thefront and back waist regions. The crotch region is that portion of thediaper which, when the diaper is worn, is generally positioned betweenthe wearer's legs.

The diaper typically comprises a topsheet 5, a backsheet 6 and anabsorbent core 7 disposed therebetween.

The topsheet may be liquid pervious. The topsheet may be at leastpartially hydrophilic. So-called apertured topsheets may also be used.Topsheets with one or more (large) openings may also be used. Thetopsheet may also include a skin care composition, e.g., a lotion. Thetopsheet may be fully or partially elasticized or may be foreshortenedto provide a void space between the topsheet and the absorbent core.Example structures including elasticized or foreshortened topsheets aredescribed in more detail in U.S. Pat. No. 5,037,416 entitled “DisposableAbsorbent Article Having Elastically Extensible Topsheet” issued toAllen et al. on Aug. 6, 1991; and U.S. Pat. No. 5,269,775 entitled“Trisection Topsheets for Disposable Absorbent Articles and DisposableAbsorbent Articles Having Such Trisection Topsheets” issued to Freelandet al. on Dec. 14, 1993.

The backsheet may be vapor pervious but liquid impervious. The backsheetmay be used to at least inhibit the fluids absorbed and contained in theabsorbent core from wetting materials that contact the absorbent articlesuch as underpants, pants, pyjamas, undergarments, and shirts orjackets, thereby acting as a barrier to fluid transport. In certainembodiments, the backsheet may be substantially impervious to liquids(e.g., urine) and comprise a laminate of a nonwoven and a thin plasticfilm such as a thermoplastic film having a thickness of about 0.012 mm(0.5 mil) to about 0.051 mm (2.0 mils). Suitable backsheet films includethose manufactured by Tredegar Industries Inc. of Terre Haute, Ind. andsold under the trade names X15306, X10962, and X10964. Other suitablebacksheet materials may include breathable materials that permit vaporsto escape from the diaper while still at least inhibiting liquidexudates from passing through the backsheet. Example breathablematerials may include materials such as woven webs, nonwoven webs,composite materials such as film-coated nonwoven webs, and microporousfilms such as manufactured by Mitsui Toatsu Co., of Japan under thedesignation ESPOIR NO and by EXXON Chemical Co., of Bay City, Tex.,under the designation EXXAIRE. Suitable breathable composite materialscomprising polymer blends are available from Clopay Corporation,Cincinnati, Ohio under the name HYTREL blend P18-3097. Such breathablecomposite materials are described in greater detail in PCT ApplicationNo. WO 95/16746, published on Jun. 22, 1995 in the name of E. I. DuPont.Other breathable backsheets including nonwoven webs and apertured formedfilms are described in U.S. Pat. No. 5,571,096 issued to Dobrin et al.on Nov. 5, 1996.

The absorbent core 7 is disposed between the topsheet and the backsheetof the absorbent article. The absorbent core may comprise one or moreabsorbent structures as disclosed herein.

The diaper may further comprise a front and back waist band and/or afastening system, typically joined to the waistband, as known in theart. Desired fastening systems comprise fastening tabs 8 and landingzones 9, wherein the fastening tabs are attached or joined to the backwaist region of the diaper and the landing zones are part of the frontwaist region of the diaper. The diaper may also have leg cuffs 10 and/orbarrier cuffs, such as elasticized barrier cuffs 11. Suitable cuffs aredescribed, for example, in U.S. Pat. No. 3,860,003; U.S. Pat. Nos.4,808,178 and 4,909; U.S. Pat. Nos. 4,695,278 and 4,795,454.

As illustrated in FIG. 1, the absorbent core may comprise an acquisitionsystem comprising an upper acquisition layer 12 and a lower acquisitionlayer 13 and optionally a core cover 14.

Processes for assembling the diaper include conventional techniquesgenerally known in the art for constructing and configuring disposableabsorbent articles. For example, the backsheet and/or the topsheet canbe joined to the absorbent core or to each other by a uniform continuouslayer of adhesive, a patterned layer of adhesive, or an array ofseparate lines, spirals, or spots of adhesive. Adhesives which have beenfound to be satisfactory are manufactured by H. B. Fuller Company of St.Paul, Minn. under the designation HL-1258 or H-2031. While the topsheet,the backsheet, and the absorbent core may be assembled in a variety ofwell-known configurations, desired diaper configurations are describedgenerally in U.S. Pat. No. 5,554,145 entitled “Absorbent Article WithMultiple Zone Structural Elastic-Like Film Web Extensible Waist Feature”issued to Roe et al. on Sep. 10, 1996; U.S. Pat. No. 5,569,234 entitled“Disposable Pull-On Pant” issued to Buell et al. on Oct. 29, 1996; andU.S. Pat. No. 6,004,306 entitled “Absorbent Article WithMulti-Directional Extensible Side Panels” issued to Robles et al. onDec. 21, 1999.

As indicated above, the absorbent core may comprise one or moreabsorbent structures that absorb and contain liquids, such as urine. Theabsorbent structure may be the absorbent core of an absorbent article ormay be part of the absorbent core of an absorbent article.

Absorbent Structure

The absorbent structure 15 is a three-dimensional structure comprising asubstrate layer 16 and an absorbent layer 17 comprising absorbentpolymer particles, and optionally cellulose, supported by, andimmobilized on, said substrate layer 16. Examples of absorbentstructures 15 are illustrated in FIGS. 2, 3B and 3C.

The substrate layer has a longitudinal dimension extending in thelongitudinal dimension of the diaper and a transverse dimensionextending in the transverse dimension of the diaper

The absorbent layer has a longitudinal dimension M extending in thelongitudinal dimension of the diaper (i.e. the absorbent layer has alength M) and a transverse dimension N extending in the transversedimension of the diaper (i.e. the absorbent layer has a width N). Theabsorbent layer possesses a central longitudinal axis x, a centraltransverse axis y perpendicular to said central longitudinal axis x, apair of opposing longitudinal edges 18 extending in the longitudinaldimension of the disposable diaper and a pair of opposing transverseedges 19 extending in the transverse dimension of the disposable diaper.The longitudinal edges or transverse edges of the absorbent layer may beparallel respectively to the central longitudinal axis or centraltransverse axis (as shown in FIG. 2) or they may follow the generaldirection of these axes while not being strictly parallel, e.g. they maybe curvilinear as for instance to provide for a narrower transversedimension in the crotch region (as shown in FIGS. 3A, 5 and 6).

The central longitudinal axis x of the absorbent layer 17 delimits tworegions of the absorbent layer referred herein as longitudinal regions20 (the plane perpendicular to the central longitudinal axis divides theabsorbent layer 17 in two longitudinal regions 20 disposed on eitherside of said plane).

One end portion of the absorbent layer is configured as a front region21 (which is the region oriented toward the front waist region of thedisposable diaper) which makes up 25% of the longitudinal dimension M ofthe absorbent layer 17. The opposite end region is configured as a backregion 22 (which is the region oriented toward the back waist region ofthe diaper) which makes up 25% of the longitudinal dimension M of theabsorbent layer 17. An intermediate portion of the absorbent layer 17 isconfigured as a crotch region 23 which makes up 50% of the longitudinaldimension M of the absorbent layer. The front, crotch and back regionsare arranged sequentially in the longitudinal dimension of the absorbentlayer.

The substrate layer of the absorbent structure may be any materialcapable to support the absorbent polymer particles. Typically, it is aweb or sheet material, such as foam, film woven and/or nonwovenmaterial. “Nonwoven material” as used herein refers to a manufacturedweb of directionally or randomly orientated fibers, bonded by friction,and/or cohesion and/or adhesion, excluding paper and products which arewoven, knitted, tufted, stitch-bonded incorporating binding yarns orfilaments, or felted by wet-milling, whether or not additionallyneedled. Nonwoven materials and processes for making them are generallyknown in the art. Generally, processes for making nonwoven materialscomprise two steps: fiber laying onto a forming surface and fiberbonding. The fiber laying step may comprise spunlaying, meltblowing,carding, airlaying, wetlaying, coform and combinations thereof. Thefiber bonding step may comprise hydroentanglement, cold calendering, hotcalendering, through air thermal bonding, chemical bonding, needlepunching, and combinations thereof. The nonwoven material may be alaminate. The laminate may comprise spunbond layer(s) (S), and/ormeltblown layer(s) (M), and/or carded layer(s) (C). Suitable laminatesinclude, but are not limited to, SS, SSS, SMS or SMMS. The nonwovenmaterial may have a basis weight from about 5 to 100 g/m², or from about10 to 40 g/m², or from about 10 to 30 g/m². Woven or nonwoven materialsmay comprise natural fibers or synthetic fibers or combinations thereof.Examples of natural fibers may include cellulosic natural fibers, suchas fibers from hardwood sources, softwood sources, or other non-woodplants. The natural fibers may comprise cellulose, starch andcombinations thereof. The synthetic fibers can be any material, such as,but not limited to, those selected from the group consisting ofpolyolefins (polypropylene and polypropylene copolymers, polyethyleneand polyethylene copolymers), polyesters (e.g., polyethyleneterephthalate), polyethers, polyamides, polyesteramides,polyvinylalcohols, polyhydroxyalkanoates, polysaccharides, andcombinations thereof. Further, the synthetic fibers can be a singlecomponent (i.e. a single synthetic material or a mixture that makes upthe entire fiber), bi-component (i.e. the fiber is divided into regions,the regions including two or more different synthetic materials ormixtures thereof and may include co-extruded fibers and core and sheathfibers) and combinations thereof. Bi-component fibers can be used as acomponent fiber of the nonwoven material, and/or they may be present toact as a binder for the other fibers present in the nonwoven material.Any or all of the fibers may be treated before, during, or aftermanufacture to change any desired properties of the fibers.

The substrate layer 16 and the absorbent layer 17 may be coextensive orthe substrate layer 16 may be slightly longer and wider than theabsorbent layer 17 (as shown in FIGS. 2, 3B and 3C.

The absorbent layer 17 comprises absorbent polymer particles 50, andoptionally cellulose. Absorbent polymer particles will be described infurther details herein below. The absorbent polymer particles may beused alone or in combination with other materials. In some embodiments,the absorbent layer comprises absorbent polymer particles combined withcellulose. “Cellulose” as used herein refers to comminuted wood pulp inthe form of fibers, typically also referred in the art as “air-felt”. Insome embodiments, the absorbent layer comprises more than 70%, or morethan 80%, or more than 90%, or more than 95% or even 100% by weight ofabsorbent polymer particles. In some other embodiments, the absorbentlayer comprises absorbent polymer particles and less than 5% by weightof cellulose, more typically less than 2% by weight of cellulose andmost typically the absorbent layer is cellulose free. In embodimentswherein the absorbent layer is cellulose free, the absorbent layercomprises only absorbent polymer particles. The resulting absorbentstructures have a reduced thickness in the dry state compared toconventional absorbent structure comprising cellulosic fibers. Thereduced thickness helps to improve the fit and comfort of the absorbentarticle for the wearer.

The absorbent layer 17 comprises at least two channels 26 substantiallyfree of absorbent polymer particles extending through the thickness ofthe absorbent layer in the longitudinal dimension of the absorbentlayer. By extending in the longitudinal dimension of the absorbentlayer, it is meant that the channels extend essentially in thelongitudinal dimension, i.e. they extend more in the longitudinaldimension than in the transverse dimension, e.g. at least twice as muchin the longitudinal dimension than in the transverse dimension. Thesetwo channels are referred herein as “longitudinal main channels”.

In addition to these two longitudinal main channels 26, the absorbentlayer 17 may comprise further channels 26′, referred herein as“secondary channels”.

“Channels” as used herein refer to discrete portions of the absorbentlayer extending through the thickness of the absorbent layer which aresubstantially free of absorbent polymer particles, i.e. no absorbentpolymer particles are intentionally present in such a channel(longitudinal main channel or secondary channel) of an absorbentstructure. However, it should be understood that, accidentally, a small,negligible amount of absorbent polymer particles may be present in thechannel, which may not contribute to the overall functionality (e.g.absorbency of the absorbent structure). Typically, the channels possesstwo transverse edges (in the shortest dimension) and two longitudinaledges (in the longest dimension) running between the transverse edges.The transverse edges of the channels may be straight (i.e. perpendicularto the longitudinal side edges), angled or curved. The channels have anaverage width w of at least 3 mm (the average of a channel is defined asthe average distance between the longitudinal side edges) or of at least4% of the width of the absorbent layer. In some embodiments, thelongitudinal channels may have complex shapes: the channels may not endwith a straight, angled or curved traverse edge but may have one or moreramifications at one or the two of their end edges (referred herein asramified channels). The ramifications also possess longitudinal edgesand one transverse edge. The channels, as well as their ramifications,have an average width w of at least 3 mm or of at least 4% of the widthof the absorbent layer.

The channels may be permanent. By permanent, it is meant that theintegrity of the channels is at least partially maintained both in drystate and wet state, i.e. the channels are resistant to frictions causedby movements of the diaper's wearer and resist wetting by bodily fluids,such as urine. Permanent channels are obtained by immobilizing theabsorbent polymer particles on the substrate layer, such as by applyinga thermoplastic adhesive material over the absorbent layer.Alternatively, the channels may be made permanent by folding thesubstrate layer into the channels or allowing the substrate layer toenter the channels so as to immobilize the absorbent polymer particlesas will be described in further details herein below.

The absorbent cores (7) of the present disclosure may comprise inparticular permanent channels formed by bonding of the first substratelayer (16) and second substrate layer (16′) through the channels.Typically, glue may be used to bond both substrate layers through thechannel, but it is possible to bond via other known means, for exampleultrasonic bonding, or heat bonding. The supporting layers can becontinuously bonded or intermittently bonded along the channels.

The Wet Channel Integrity Test described below can be used to test ifchannels are permanent following wet saturation and to what extent.

Wet Channel Integrity Test

This test is designed to check the integrity of a channel following wetsaturation. The test can be performed directly on an absorbent structureor on an absorbent core containing the absorbent structure.

-   -   1. The length (in millimeters) of the channel is measured in the        dry state (if the channel is not straight, the curvilinear        length through the middle of the channel is measured).    -   2. The absorbent structure or core is then immersed in 5 liters        of synthetic urine “Saline”, with a concentration of 9.00 g NaCl        per 1000 ml solution prepared by dissolving the appropriate        amount of sodium chloride in distilled water. The temperature of        the solution must be 20+/−5° C.    -   3. After 1 minute in the saline, the absorbent structure or core        is removed and held vertically by one end for 5 seconds to        drain, then extended flat on a horizontal surface with the        garment-facing side down, if this side is recognizable. If the        absorbent structure or core comprises stretch elements, the        absorbent structure or core is pulled taut in both X and Y        dimensions so that no contraction is observed. The        extremes/edges of the absorbent structure or core are fixed to        the horizontal surface, so that no contraction can happen.    -   4. The absorbent structure or core is covered with a suitably        weighted rigid plate, with dimensions as follows: length equal        to the extended length of the absorbent structure or core, and        width equal to the maximum absorbent structure or core width in        the cross direction.    -   5. A pressure of 18.0 kPa is applied for 30 seconds over the        area of the rigid plate above mentioned. Pressure is calculated        on the basis of overall area encompassed by the rigid plate.        Pressure is achieved by placing additional weights in the        geometric center of the rigid plate, such that the combined        weight of the rigid plate and the additional weights result in a        pressure of 18.0 kPa over the total area of the rigid plate.    -   6. After 30 seconds, the additional weights and the rigid plate        are removed.    -   7. Immediately afterwards, the cumulative length of the portions        of the channel which remained intact is measured (in        millimeters; if the channel is not straight, the curvilinear        length through the middle of the channel is measured). If no        portions of the channel remained intact then the channel is not        permanent.    -   8. The percentage of integrity of the permanent channel is        calculated by dividing the cumulative length of the portions of        the channel which remained intact by the length of the channel        in the dry state, and then multiplying the quotient by 100.

Advantageously, a permanent channel according to the present disclosurehas a percentage of integrity of at least 20%, or 30%, or 40%, or 50%,or 60, or 70%, or 80%, or 90% following this test.

When the absorbent structure comprises absorbent polymer particles andcellulose, it may be desired that said channels, i.e. longitudinal mainchannels and/or secondary channels, are also free of such cellulose.

In the following, when applicable, the description applies to eachchannel taken independently. For example, by “two longitudinal channelsmay extend over a distance L which is at least 15%”, it is meant thateach of the two longitudinal channels may extend over a distance L whichis at least 15% . . . ”, i.e. the channels may be the same or different.

Longitudinal Main Channels

The two longitudinal main channels 26 may be distributed in theabsorbent layer 17 such that each longitudinal portion 20 of theabsorbent layer comprises one longitudinal main channel 26.

As shown in FIG. 2, the two longitudinal main channels are at leastpresent in the crotch region of the absorbent layer. By “at leastpresent in the crotch region”, it is meant that the channels may be onlypresent in the crotch region or they may extend from the crotch regionup to the front region and/or up to the back region, i.e. they mayextend beyond the crotch region. In some embodiments, the twolongitudinal main channels may extend across at least 15%, or at least20% or at least 30% and up to 50%, or up to 70% or up 90% of thelongitudinal dimension of the absorbent layer (i.e. they may extend overa distance L which is at least 15% and up to 50%, or up to 70% or up 90%of the length M of the absorbent layer). In some embodiments, the twolongitudinal main channels may be present only in the crotch region.When present only in the crotch region, the longitudinal main channelsmay extend over the whole longitudinal dimension of the crotch region,i.e. 50% of the longitudinal dimension M of the absorbent layer, or theymay extend in only part of the crotch region, i.e. from at least 15%, orat least 20% or at least 30% to 40%, or to 45% or to less than 50% ofthe longitudinal dimension of the absorbent layer. In some embodiments,the two longitudinal main channels 26 may be present in the crotchregion, or part thereof, and part of the front region and/or part of theback region (such as shown in FIG. 2). In some embodiments, thelongitudinal main channels may be present in the front and crotchregions, i.e. the channels extend through the crotch region (or partthereof) and part of the front region. In these embodiments, thelongitudinal main channels may extend up to 70% of the longitudinaldimension of the absorbent layer, typically from 15%, or from 30%, orfrom 35% or from 40% to 70% of the longitudinal dimension of theabsorbent layer (i.e. they may extend over a distance L which is up to70% of the length M of the absorbent layer). In some embodiments, thelongitudinal main channels may be present in the back and crotchregions, i.e. the channels extend through the crotch region (or partthereof) and part of the back region. In these embodiments, thelongitudinal main channels may extend up to 70% of the longitudinaldimension of the absorbent layer, typically from 15%, or from 30%, orfrom 35% or from 40% to 70% of the longitudinal dimension of theabsorbent layer (i.e. they may extend over a distance L which is up to70% of the length M of the absorbent layer). In some embodiments, thelongitudinal main channels may be present in the front, crotch and backregions. In these embodiments, the longitudinal main channels may extendup to 90% of the longitudinal dimension M of the absorbent layer,typically from 55% or from 60% to 70%, or to 80% of the longitudinaldimension of the absorbent layer (i.e. they may extend over a distance Lwhich is up to 90% of the length M of the absorbent layer).

The longitudinal main channels 26 may be mirror images of one anotherwith respect to the central longitudinal axis x of the absorbent layer17, i.e. the longitudinal main channel in one longitudinal region 20 maybe mirror image of the longitudinal main channel in the otherlongitudinal region of the absorbent layer 17.

The longitudinal main channels 26 may not extend up to the transverseedges 19 of the absorbent layer 17, i.e. from one transverse edge to theother. Typically, the absorbent layer comprises, along each transverseedge and immediately adjacent to said edge, a strip free of channelswhich extends in the transverse dimension of the absorbent layer fromone longitudinal edge to the other. Said strips have respectively awidth F′ or G′ which is at least 5% of the longitudinal dimension of theabsorbent layer (i.e. a width which is at least 5% of the length of theabsorbent layer). In other words, the smallest distance F′ or G′ betweenthe edge of a channel and the transverse edge of the absorbent layer isat least 5% of the longitudinal dimension M of the absorbent layer. Insome embodiments, the width F′ or G′ is at least from 5% to 15%, or to10% of the longitudinal dimension of the absorbent layer.

Furthermore, in order to reduce the risk of fluid leakages and run-off,the longitudinal main channels may not extend up to the longitudinaledges 18 of the absorbent layer 17. Typically, the absorbent layercomprises, along each longitudinal edge and immediately adjacent to saidedge, a strip free of channel which extends in the longitudinaldimension of the absorbent layer from one transverse edge to the other.Said strips have respectively a width I′ or F′ which is at least 5%, orat least 10%, or at least 12% to 25% of the transverse dimension N ofthe absorbent layer in a given region (i.e. a width I′ or F′ which is atleast 5% of the width N of the absorbent layer). In other words, theminimum distance I′ or F′ between the edge of a channel and thelongitudinal edge of the absorbent layer is at least from 5% to 25% ofthe transverse dimension of the absorbent layer. For example, thedistance I′ or F′ in the crotch region may correspond to at least 5%, orto at least 10% or at least 12% of the transverse dimension N of theabsorbent layer in said crotch region. In some embodiments, the distanceI′ and/or F′ is of 10 mm, or 15 mm or 20 mm.

The longitudinal main channels may be straight channels running parallelto the longitudinal axis of the absorbent layer (as shown schematicallyin FIG. 4A). Straight channels act as folding lines in the absorbentstructure which contribute to provide a desirable bucket shape to thediaper once worn. The diaper once worn conforms to the inside of thewearer's tight. As a result, a U-like shape is achieved which minimizesleakage and increases comfort. These channels also improve fluidtransportation within the absorbent structure and therefore contributeto fast insult acquisition.

Alternatively, the longitudinal main channels may be curved, as shown inFIG. 4B. Curved channels act as folding lines in the absorbent structurewhich assist the absorbent structure in following the morphology of thediaper's wearer, i.e. the channels constrain the product to take aU-like shape when the diaper is worn and compressed by the wearer'stights. Thus, the channels provide a comfortable and superior fit inaddition to permitting improved liquid transportation.

The longitudinal main channels 26 may be oblique channels, as shown inFIG. 4C, i.e. straight channels oriented under an angle θ of up to 30degrees, or up to 20 degrees, or up to 10 degrees with respect to thelongitudinal central axis of the absorbent structure.

In some other alternatives, the longitudinal main channels may be angledchannels, as shown in FIG. 4D. Angled channels are channels made of twoor more portions connected under an angle σ to one another. Typically,angled channels are made of two portions connected under an angle α ofat least 150 degrees, or at least 160 degrees or at least 170 degrees.

In some embodiments, the longitudinal main channels may be so-called“ramified” channels, i.e. channels having at least one extremity whichmay not end with a straight, angled or curved transverse edge 28 butwith a ramification 29. The ramification 29 may form an angle α of up to30 degrees, or up to 20 degrees or up to 10 degrees with respect to thelongitudinal central axis of the channel.

The longitudinal main channels 26 may have an average width w of from 3mm to 15 mm, or from 4 mm to 14 mm or from 5 mm to 12 mm (the averagewidth of a channel is the average distance between its longitudinal sideedges 27). The average width of the longitudinal main channels may be atleast 4% of the width of the absorbent layer, or at least 7% and up to15%, or 20% or 25%. In some embodiments, the longitudinal main channelsmay have an average width w of from 3 mm to 18 mm, or from 5 mm to 15 mmor from 6 to 10 mm. The ramifications 29, as well, have an average widthw of at least 3 mm or of at least 4% of the width of the absorbentlayer, or of at least 7% and up to 15%, or up to 20% or up to 25%(average distance between the longitudinal edges 27′ of theramifications 29).

The longitudinal main channels 26 may be separated in the crotch regionby a distance D (shown in FIG. 2) of at least 5%, or at least 10%, or atleast 20%, or at least 25% of the transverse dimension (width) of theabsorbent layer in said crotch region. It was found that when these twolongitudinal main channels are separated by a distance of at least 5% ofthe transverse dimension of the absorbent layer in the crotch region,the disposable diaper takes a desirable bucket shape which improves thefit of the diaper. In some embodiments, the longitudinal main channelsmay be separated in the crotch region by a distance of at least 10 mm,or at least 15 mm, or at least 20 mm, or at least 30 mm. In someembodiments, the distance separating the longitudinal main channels inthe crotch region is from 20 to 30 mm.

The inventors have found that when an absorbent structure is providedwith at least two channels as described above, i.e. two longitudinalmain channels, the flexibility of the absorbent structure is increased,especially for absorbent structure comprising exclusively absorbentpolymer particles in the absorbent layer. The two channels createbending lines which drive the bending of the diaper to conform to thewearer's anatomy and therefore improve the fit of the diaper.

Furthermore, the inventors observed that absorbent structure having atleast two channels as described above exhibit better fluidtransportation versus absorbent structure of the same type notcomprising channels. Indeed, it was observed that the channels providefor fast insults acquisition which reduces risk of leakages. Thechannels avoid saturation of the absorbent layer in the region of fluiddischarge which increases the risk of leakages.

Secondary Channels

The absorbent layer may comprise further channels 26′ to furtherincrease the fluid transportation and/or fit of the absorbent article,referred herein as secondary channels. The above description of thelongitudinal main channels may equally apply to any of said secondarychannels 26′. However, in some embodiments, the secondary channels maybe shorter than the main longitudinal channels.

The secondary channels may extend in the longitudinal dimension of theabsorbent layer (longitudinal secondary channels) and/or in thetransverse dimension of the absorbent layer (transverse secondarychannels), provided they do not extend up to the longitudinal edgesand/or transverse edges of the absorbent layer. Thus, the absorbentlayer is free of channels, i.e. longitudinal main channels and secondarychannels, extending up to its longitudinal edges and its transverseedges.

The longitudinal secondary channels may extend over a distance V′ of atleast 10%, or at least 15%, or at least 20% of the longitudinaldimension M of the absorbent layer (as shown in FIG. 6). They may extendup to 90% of the longitudinal dimension of the absorbent layer.Typically, the longitudinal secondary channels extend up to 30% or 45%of the longitudinal dimension of the absorbent layer.

Transverse secondary channels may extend over a distance of at least10%, or at least 15%, or at least 20%, of the transverse dimension(width) N of the absorbent layer. They may extend up to 90% of thetransverse dimension of the absorbent layer. Typically, the transversesecondary channels extend up to 30% or 45% of the transverse dimensionof the absorbent layer. In some embodiments, the absorbent layer may notcomprise transverse channels.

Typically, the secondary channels are distributed such that along eachtransverse edge of the absorbent layer and immediately adjacent to saidedge, the strip which extends in the transverse dimension of theabsorbent layer from one longitudinal edge to the other over a distanceF′ or G′ remains free of channels (as disclosed above in respect of thelongitudinal main channels distribution).

Typically, the secondary channels are distributed such that along eachlongitudinal edge and immediately adjacent to said edge, the strip whichextends in the longitudinal dimension of the absorbent layer from onetransverse edge to the other over a distance H′ or I′ remains free ofchannels (as disclosed above in respect of the longitudinal mainchannels distribution).

The longitudinal main channels and, when present, the secondary channelsmay be distributed in the absorbent layer such that a strip extendingalong the central longitudinal axis of the absorbent layer (andincluding said axis) from one transverse edge to the other one, andhaving a width D′ of at least 5%, or at least 10% and up to 60%, or upto 70%, or up to 75% of the transverse dimension of the absorbent layerremains free of channels. The absorbent polymer particles may becontinuously present in said strip. For example, said strip may have awidth D′ of at least 5 mm, or at least 10 mm, or at least 15 mm or 20 mmand up to 70 mm or up to 40 mm. The absence of channels in said strip isadvantageous since it at least inhibits the diaper from taking aninverted V-shape configuration once worn. Inverted V-shape configurationincreases the risk of fluid leakages. In some embodiments, the averagebasis weight of absorbent polymer particles in said strip is high, i.e.at least 350 gsm and up to 1000 gsm, or for example from 450 gsm to 750gsm.

Although the secondary channels may be transverse secondary channels,the absorbent layer may not comprise any such channels in the crotchregion. Channels extending in the transverse dimension in the crotchregion would transport liquids to the transverse edges and wouldincrease undesirably the risk of fluid leakages and/or run off. However,such secondary channels may be present in the front region and/or backregion of the absorbent layer.

Longitudinal secondary channels may be present in the front region, backregion and/or crotch region of the absorbent layer.

As disclosed in respect of the longitudinal main channels, the secondarychannels may be straight channels parallel to the longitudinal centralaxis of the absorbent structure (as shown in FIG. 4A), curved channels(as shown in FIG. 4B), angled channels (as shown in FIG. 4D), obliquechannels (as shown in FIG. 4C) or ramified channels (as shown in FIG.4E). Oblique longitudinal channels, when present in the front or backregion of the absorbent layer (i.e. not in the crotch region), may forman angle θ of up to 60 degrees, or up to 50 degrees, or up to 45 degreeswith the longitudinal central axis of the absorbent layer.

The secondary channels may have an average width w′ of from 3 mm to 15mm, or from 4 mm to 14 mm or from 5 mm to 12 mm (the average width of achannel is the average distance between its longitudinal side edges 27)or the average width of the secondary channels may be at least 4% of thewidth of the absorbent layer, or at least 7% and up to 15%, or 20% or25%. In some embodiments, the secondary channels may have an averagewidth w′ of from 3 mm to 18 mm, or from 5 mm to 15 mm or from 6 to 10mm. The ramifications 29, as well, have an average width w′ of at least3 mm or of at least 4% of the width of the absorbent layer, or at least7% and up to 15%, or up to 20% or up to 25% (average distance betweenthe longitudinal edges 27′ of the ramifications 29).

The longitudinal main channels and secondary channels may be spacedapart from each other by a distance of at least 5 mm, or at least 8 mm.

The absorbent layer may comprise one or more of said secondary channels,such as 2, 3, 4, 5 or 6. The absorbent layer may comprise an even numberof secondary channels. The secondary channels may be distributed in theabsorbent layer such that each longitudinal region of the absorbentlayer comprises an equal number of secondary channels. In someembodiments, the longitudinal regions comprising the channels (i.e. mainlongitudinal channels and secondary channels) are mirror images of eachother with respect to the central longitudinal axis of the absorbentlayer.

In some embodiments, such as illustrated in FIGS. 3A to 3C, thelongitudinal secondary channels and main longitudinal channels are notdistinguishable, i.e. the longitudinal secondary channels and mainlongitudinal channels are similar. The resulting absorbent layer maythus be seen as comprising more than two longitudinal main channels 26which are at least present in the crotch region (e.g. 4 longitudinalmain channels). In some embodiments, it may be desired that the maximalnumber of channels in the crotch region is such that the sum of thewidths w of the channels 26 is less than 50% of the transverse dimension(width) of the absorbent layer in the crotch region.

In some embodiments, such as shown in FIG. 5, the absorbent layer 17 maycomprise two main longitudinal channels 26 as described above and twosecondary longitudinal channels in the front region 26′. The two mainlongitudinal channels 26 are at least present in the crotch region. Byat least present in the crotch region, it is meant that said two mainlongitudinal channels may extend up the front region and/or back region.The two main longitudinal channels 26 at least present in the crotchregion may extend over a distance L which is at least 15% of thelongitudinal dimension M of the absorbent layer. The secondarylongitudinal channels 26′ in the front region may extend over a distanceV′ which is at least 10% to 20% of the longitudinal dimension M of theabsorbent layer. The two main longitudinal channels 26 in the crotchregion may be curved channels whereas the two secondary longitudinalchannels 26′ in the front region may be oblique channels. The channelsin one of the longitudinal regions may be mirror images of each other inthe other longitudinal region.

In some other embodiments, such as shown in FIG. 6, the absorbent layer17 may comprise two longitudinal main channels 26 in the crotch region,two longitudinal secondary channels 26′ in the front region and twolongitudinal secondary channels 26′ in the back region. The longitudinalmain channels 26 in the crotch region 25 may extend across at least 15%of the longitudinal dimension of the absorbent layer. The longitudinalsecondary channels 26′ in the front region and back region may extendover a distance V′ which is at least 10% to 20% of the longitudinaldimension M of the absorbent layer. The longitudinal main channels 26 inthe crotch region may be curved channels whereas the longitudinalsecondary channels 26′ in the front region and back region may beoblique channels. The channels in one of the longitudinal regions may bemirror images of each other in the other longitudinal region.

When the secondary channels 26′ are longitudinal secondary channelsextending in the crotch region, it may be desired that the maximalnumber of channels in the absorbent layer is such that the sum of thewidths w and w′ of the channels (secondary channels and mainlongitudinal channels) is less than 50% of the transverse dimension ofthe absorbent layer in the crotch region.

In some embodiment herein, it may be desired that the region 30 of theabsorbent layer immediately adjacent the channels 26 and 26′ andextending over a distance k of at least 3 mm, or of at least 5 mm, or ofat least 7 mm from the edges of the channels comprises absorbent polymerparticles present substantially continuously. In these regions 30, theaverage basis weight of absorbent polymer particles may be high, i.e. atleast 350 gsm, or at least 400 gsm, or at least 500 gsm or at least 600gsm.

Absorbent Layer

As explained above, channels 26 and 26′ are regions free of absorbentpolymer particles extending through the thickness of the absorbentlayer. The absorbent layer comprises absorbent polymer particles 50alone or in combination with other materials such as cellulose. Theabsorbent layer may comprise only absorbent polymer particles. Theabsorbent polymer particles are immobilized on the substrate layer,typically by a thermoplastic adhesive material 40.

Typically the absorbent polymer particles suitable for use in theabsorbent layer can comprise any absorbent polymer particles known fromsuperabsorbent literature, for example such as described in ModernSuperabsorbent Polymer Technology, F. L. Buchholz, A. T. Graham, Wiley1998.

The absorbent polymer particles may be spherical, spherical-like orirregular shaped particles, such as Vienna-sausage shaped particles, orellipsoid shaped particles of the kind typically obtained from inversephase suspension polymerizations. The particles can also be optionallyagglomerated at least to some extent to form larger irregular particles.

The absorbent polymer particles can be selected among polyacrylates andpolyacrylate based materials that are internally and/or surfacecross-linked, such as for example partially neutralized cross-linkedpolyacrylates or acid polyacrylate. Examples of absorbent polymerparticles suitable in the present disclosure are described for instancein the PCT Patent Application WO 07/047598, WO 07/046052, WO2009/155265and WO2009/155264.

The absorbent polymer particles may be internally cross-linked, i.e. thepolymerization is carried out in the presence of compounds having two ormore polymerizable groups which can be free-radically copolymerized intothe polymer network. Useful crosslinkers include for example ethyleneglycol dimethacrylate, diethylene glycol diacrylate, allyl methacrylate,trimethylolpropane triacrylate, triallylamine, tetraallyloxyethane asdescribed in EP-A 530 438, di- and triacrylates as described in EP-A 547847, EP-A 559 476, EP-A 632 068, WO 93/21237, WO 03/104299, WO03/104300, WO 03/104301 and in DE-A 103 31 450, mixed acrylates which,as well as acrylate groups, include further ethylenically unsaturatedgroups, as described in DE-A 103 31 456 and DE-A 103 55 401, orcrosslinker mixtures as described for example in DE-A 195 43 368, DE-A196 46 484, WO 90/15830 and WO 02/32962 as well as cross-linkersdescribed in WO2009/155265.

The absorbent polymer particles may be externally cross-linked (postcross-linked). Useful post-crosslinkers include compounds including twoor more groups capable of forming covalent bonds with the carboxylategroups of the polymers. Useful compounds include for example alkoxysilylcompounds, polyaziridines, polyamines, polyamidoamines, di- orpolyglycidyl compounds as described in EP-A 083 022, EP-A 543 303 andEP-A 937 736, polyhydric alcohols as described in DE-C 33 14 019, cycliccarbonates as described in DE-A 40 20 780, 2-oxazolidone and itsderivatives, such as N-(2-hydroxyethyl)-2-oxazolidone as described inDE-A 198 07 502, bis- and poly-2-oxazolidones as described in DE-A 19807 992, 2-oxotetrahydro-1,3-oxazine and its derivatives as described inDE-A 198 54 573, N-acyl-2-oxazolidones as described in DE-A 198 54 574,cyclic ureas as described in DE-A 102 04 937, bicyclic amide acetals asdescribed in DE-A 103 34 584, oxetane and cyclic ureas as described inEP-A 1 199 327 and morpholine-2,3-dione and its derivatives as describedin WO 03/031482.

The absorbent polymer particles may have surface modifications, such asbeing coated or partially coated with a coating agent. Examples ofcoated absorbent polymer particles are disclosed in WO2009/155265. Thecoating agent may be such that it renders the absorbent polymerparticles more hydrophilic. The coating agent may be a polymer, such asan elastic polymer or a film-forming polymer or an elastic film-formingpolymer, which forms an elastomeric (elastic) film coating on theparticle. The coating may be a homogeneous and/or uniform coating on thesurface of the absorbent polymer particles. The coating agent may beapplied at a level of from 0.1% to 5%, or from 0.2% to 1% by weight ofthe surface-modified absorbent polymer particles.

Typically, the absorbent polymer particles may have a selected particlesize distribution. For example, the absorbent polymer particles may havea particle size distribution in the range from 45 μm to 4000 μm, morespecifically from 45 μm to about 1000 μm, or from about 100 μm to about850 μm, or from about 100 μm to about 600 μm. The particle sizedistribution of a material in particulate form can be determined as itis known in the art, for example by means of dry sieve analysis (EDANA420.02 “Particle Size distribution). Optical methods, e.g. based onlight scattering and image analysis techniques, can also be used.

The absorbent layer of the absorbent structure may comprise absorbentpolymer particles, and optionally cellulose, distributed on thesubstrate layer such as to form as a continuous layer, i.e. anuninterrupted layer of absorbent polymeric particles and cellulose whenpresent, which nevertheless comprises regions substantially free ofabsorbent polymer particles. These discrete regions substantially freeof absorbent particles correspond to the channels of the absorbentstructure. In some embodiments, the absorbent layer is cellulose free.Alternatively, the absorbent layer may comprise absorbent polymerparticles, and optionally cellulose, distributed on the substrate layersuch as to form a discontinuous layer. In some embodiments, theabsorbent layer is cellulose free. In these embodiments, the absorbentpolymer particle and cellulose when present, may be deposited on thesubstrate layer in clusters of particles (and cellulose when present),thus forming a discontinuous layer or an interrupted layer of absorbentpolymer particles (and cellulose when present) which neverthelesscomprises regions substantially free of clusters of absorbent polymerparticles. These discrete regions substantially free of clusters ofabsorbent particles correspond to the channels of the absorbentstructure. The clusters of absorbent polymer particles (and cellulosewhen present) may have a variety of shape including, but not limited to,circular, oval, square, rectangular, triangular and the like. Suitablemethods for depositing particles in cluster of particles are disclosedin EP 1621167 A2, EP 1913914 A2 and EP 2238953 A2. Typically, absorbentpolymer particles are deposited on the substrate layer in clusters ofparticles when two such absorbent structures are combined to form anabsorbent core. The two absorbent structures are combined such that theresulting absorbent core comprises absorbent polymer particlessubstantially continuously distributed between the two substrate layers,except in regions where channels are present. “Substantiallycontinuously distributed” as used herein indicates that the firstsubstrate layer and second substrate layer are separated by amultiplicity of absorbent polymer particles. It is recognized that theremay be minor incidental contact areas between the first substrate layerand second substrate layer within the absorbent particulate polymermaterial area (i.e. area between the two substrate layers). Incidentalcontact areas between the first substrate and second substrate may beintentional or unintentional (e.g. manufacturing artifacts) but may notform geometries such as pillows, pockets, tubes, quilted patterns andthe like.

The absorbent polymer particles may be immobilized on the substratelayer. Immobilization may be achieved by applying a thermoplasticadhesive material which holds and immobilizes the absorbent polymerparticles, and cellulose when present, on the substrate layer. Somethermoplastic adhesive material may also penetrate into the layer ofabsorbent polymer particles and into the substrate layer to providefurther immobilization and affixation. The thermoplastic adhesivematerial may not only help in immobilizing the absorbent polymerparticles on the substrate layer but also helps in maintaining theintegrity of the channels. The thermoplastic adhesive material avoidsthat a significant amount of absorbent polymer particles migrates intothe channels.

Integrity/immobilization of the channels may also be achieved byallowing the substrate layer supporting the absorbent polymer particlesto fold into the channels, i.e. undulate into the channels.Alternatively, integrity/immobilization may be achieved by allowing afurther substrate layer, such as the core cover when present, to foldinto the channels, i.e. undulate into the channels. When two absorbentstructures as disclosed above are combined, integrity/immobilization maybe achieved by allowing the substrate layer of one of the absorbentstructures to fold into the channels. In some embodiments, an adhesive(e.g. a thermoplastic adhesive material) may be applied on theseportions of the substrate layer which undulates into the channels toprovide further affixation.

The thermoplastic adhesive material may be applied as a continuous layer(i.e. uniformly) over the absorbent layer. In some embodiments, thethermoplastic adhesive material contacts the absorbent polymer particles(and cellulose when present) and part of the substrate layer when theabsorbent polymer particles (and cellulose when present) are depositedin clusters.

In some embodiments, the thermoplastic adhesive material may be appliedas a fibrous layer forming a fibrous network over the absorbent layer.The thermoplastic adhesive fibrous layer may be at least partially incontact with the absorbent polymer particles (and cellulose whenpresent) and partially in contact with the substrate layer of theabsorbent structure when the absorbent polymer particles (and cellulosewhen present) are deposited in clusters. Thereby, the thermoplasticadhesive material may provide cavities to cover the absorbent polymerparticles, and thereby immobilizes this material and the channels whenpresent.

Thermoplastic adhesive materials suitable for immobilizing the absorbentpolymer particles typically combine good cohesion and good adhesionbehavior. Good adhesion promotes good contact between the thermoplasticadhesive material and the absorbent polymer particles and the substratelayer. Good cohesion reduces the likelihood that the adhesive breaks, inparticular in response to external forces, and namely in response tostrain. When the absorbent structure/core absorbs liquid, the absorbentpolymer particles swell and subject the thermoplastic adhesive materialto external forces. The thermoplastic adhesive material may allow forsuch swelling, without breaking and without imparting too manycompressive forces, which would restrain the absorbent polymer particlesfrom swelling.

Thermoplastic adhesive materials suitable for use in the presentdisclosure includes hot melt adhesives comprising at least athermoplastic polymer in combination with a plasticizer and otherthermoplastic diluents such as tackifying resins and additives such asantioxidants. Example suitable hot melt adhesive materials are describedin EP 1447067 A2. In some embodiments, the thermoplastic polymer has amolecular weight (Mw) of more than 10,000 and a glass transitiontemperature (Tg) below room temperature or −6° C.>Tg<16° C. In certainembodiments, the concentrations of the polymer in a hot melt are in therange of about 20 to about 40% by weight. In certain embodiments,thermoplastic polymers may be water insensitive. Example polymers are(styrenic) block copolymers including A-B-A triblock structures, A-Bdiblock structures and (A-B)n radial block copolymer structures whereinthe A blocks are non-elastomeric polymer blocks, typically comprisingpolystyrene, and the B blocks are unsaturated conjugated diene or(partly) hydrogenated versions of such. The B block is typicallyisoprene, butadiene, ethylene/butylene (hydrogenated butadiene),ethylene/propylene (hydrogenated isoprene), and mixtures thereof.

Other suitable thermoplastic polymers that may be employed aremetallocene polyolefins, which are ethylene polymers prepared usingsingle-site or metallocene catalysts. Therein, at least one comonomercan be polymerized with ethylene to make a copolymer, terpolymer orhigher order polymer. Also applicable are amorphous polyolefins oramorphous polyalphaolefins (APAO) which are homopolymers, copolymers orterpolymers of C2 to C8 alpha olefins.

The thermoplastic adhesive material, typically a hot-melt adhesivematerial, is generally present in the form of fibres, i.e. the hot meltadhesive can be fiberized. In some embodiments, the thermoplasticadhesive material forms a fibrous network over the absorbent polymerparticles. Typically, the fibres can have an average thickness fromabout 1 μm to about 100 μm, or from about 25 μm to about 75 μm, and anaverage length from about 5 mm to about 50 cm. In particular the layerof hot melt adhesive material can be provided such as to comprise anet-like structure. In certain embodiments the thermoplastic adhesivematerial is applied at an amount of from 0.5 to 30 g/m², or from 1 to 15g/m², or from 1 and 10 g/m² or even from 1.5 and 5 g/m² per substratelayer.

A typical parameter for a hot melt adhesive suitable for use in thepresent disclosure can be a loss angle tan Delta at 60° C. of below thevalue of 1, or below the value of 0.5. The loss angle tan Delta at 60°C. is correlated with the liquid character of an adhesive at elevatedambient temperatures. The lower tan Delta, the more an adhesive behaveslike a solid rather than a liquid, i.e. the lower its tendency to flowor to migrate and the lower the tendency of an adhesive superstructureas described herein to deteriorate or even to collapse over time. Thisvalue is hence particularly important if the absorbent article is usedin a hot climate.

It may be beneficial, e.g. for process reasons and/or performancereasons, that the thermoplastic adhesive material has a viscosity ofbetween 800 and 4000 mPa·s, or from 1000 mPa·s or 1200 mPa·s or from1600 mPa·s to 3200 mPa·s or to 3000 mPa·s or to 2800 mPa·s or to 2500mPa·s, at 175° C., as measurable by ASTM D3236-88, using spindle 27, 20pmp, 20 minutes preheating at the temperature, and stirring for 10 min.

The thermoplastic adhesive material may have a softening point ofbetween 60° C. and 150° C., or between 75° C. and 135° C., or between90° C. and 130° C., or between 100° C. and 115° C., as can be determinedwith ASTM E28-99 (Herzog method; using glycerine).

In one embodiment herein, the thermoplastic adhesive component may behydrophilic, having a contact angle of less than 90°, or less than 80°or less than 75° or less than 70°, as measurable with ASTM D 5725-99.

In some embodiments, the absorbent structure may also comprise anadhesive material deposited on the substrate before application of theabsorbent polymer particles on the substrate layer, referred herein asthe auxiliary adhesive. The auxiliary adhesive may enhance theimmobilization of the absorbent polymer particles on the substratelayer. It may be a thermoplastic adhesive material, and comprise thesame thermoplastic adhesive material as described hereinabove or it maybe different. An example of commercially available adhesive is H.B.Fuller Co. (St. Paul, Minn.) Product No. HL-1620-B. The thermoplasticadhesive material may be applied to the substrate layer by any suitablemeans.

In some embodiments, the absorbent polymer particles, and optionallycellulose, may be distributed evenly in the longitudinal and/ortransverse dimensions of the absorbent layers irrespective of whetherthe absorbent layer is a continuous layer or a discontinuous layer ofabsorbent polymer particles, and optionally cellulose, as describedabove to provide an absorbent core having an even distribution ofabsorbent polymer particles. The average basis weight of absorbentpolymer particles may depend on the particular diaper in which it may beincorporated. In some embodiments, the average basis weight of absorbentpolymer particles in the absorbent core may be from 350 gsm to 1500 gsm.The amount of absorbent polymeric particles in the respective region iscalculated by determining the weight of absorbent polymeric material inthis region and dividing it by the total surface area of the region(hence, the average amount is taken).

In some embodiments, the absorbent polymer particles, and optionallycellulose, may be distributed unevenly in the longitudinal and/ortransverse dimension of at least one of the absorbent layers to providea profiled absorbent core. For example, the crotch region of theabsorbent structure/core may comprise a higher amount of absorbentpolymer particles per area compared to the front and back regions of theabsorbent structure/core. In some embodiment, the front half of theabsorbent core comprises most of the absorbent capacity, i.e. it maycomprise more than about 60% of the absorbent polymer particles, or morethan about 65%, or more than 70%, based on the total weight of absorbentpolymer particles in the absorbent core.

In some embodiments, the absorbent structure as disclosed above may formthe absorbent core of the disposable diaper or may be a componentthereof (i.e. the absorbent core may be a laminate of absorbentstructures).

The absorbent core may further comprise a cover layer, typicallydisposed on the thermoplastic adhesive material. The cover layer may bea separate layer or it may be unitary with the substrate layer. In sucha case, the substrate layer supporting the absorbent polymer particlesis folded to form a top and bottom layer which encloses the absorbentpolymer particles. The cover layer may be provided of the same materialas the substrate layer, or may be provided of a different material. Thelayers may be bonded together at about the periphery to enclose theabsorbent polymer particles therein, e.g. by adhesive bonding and/orheat bonding. In some embodiments, the core cover may undulate into thechannels.

In some embodiments, the absorbent core may comprise an acquisitionsystem which is disposed between the topsheet and the wearer facing sideof the absorbent structure. The acquisition system may serve as atemporary reservoir for liquid until the absorbent structure can absorbthe liquid. The acquisition system may comprise a single layer ormultiple layers, such as an upper acquisition layer facing towards thewearer's skin and a lower acquisition layer facing the garment of thewearer. The acquisition system may be in direct contact with theabsorbent structure. In these embodiments, the acquisition system mayfill in the channels or part thereof. In some embodiments, theacquisition system may be placed on top of the core cover when present.In embodiments wherein the core cover or substrate layer folds into thechannels, i.e. undulates into the channels, the acquisition system mayfill in the channels or part thereof. In some embodiments, theacquisition system, or one layer thereof, may be bonded to the corecover or substrate layer which undulates into the channels thusproviding an undulating profile to said acquisition system.

In a certain embodiment, the acquisition system may comprise chemicallycross-linked cellulosic fibers. Such cross-linked cellulosic fibers mayhave desirable absorbency properties. Example chemically cross-linkedcellulosic fibers are disclosed in U.S. Pat. No. 5,137,537. In certainembodiments, the chemically cross-linked cellulosic fibers arecross-linked with between about 0.5 mole % and about 10.0 mole % of a C2to C9 polycarboxylic cross-linking agent or between about 1.5 mole % andabout 6.0 mole % of a C2 to C9 polycarboxylic cross-linking agent basedon glucose unit. Citric acid is an example cross-linking agent. In otherembodiments, polyacrylic acids may be used. Further, according tocertain embodiments, the cross-linked cellulosic fibers have a waterretention value of about 25 to about 60, or about 28 to about 50, orabout 30 to about 45. A method for determining water retention value isdisclosed in U.S. Pat. No. 5,137,537. According to certain embodiments,the cross-linked cellulosic fibers may be crimped, twisted, or curled,or a combination thereof including crimped, twisted, and curled.

In a certain embodiment, one or both of the upper and lower acquisitionlayers may comprise a non-woven, which may be hydrophilic. Further,according to a certain embodiment, one or both of the upper and loweracquisition layers may comprise the chemically cross-linked cellulosicfibers, which may or may not form part of a nonwoven material. Accordingto an example embodiment, the upper acquisition layer may comprise anonwoven, without the cross-linked cellulosic fibers, and the loweracquisition layer may comprise the chemically cross-linked cellulosicfibers. Further, according to an embodiment, the lower acquisition layermay comprise the chemically cross-linked cellulosic fibers mixed withother fibers such as natural or synthetic polymeric fibers. According toexample embodiments, such other natural or synthetic polymeric fibersmay include high surface area fibers, thermoplastic binding fibers,polyethylene fibers, polypropylene fibers, PET fibers, rayon fibers,lyocell fibers, and mixtures thereof. Suitable non-woven materials forthe upper and lower acquisition layers include, but are not limited toSMS material, comprising a spunbonded, a melt-blown and a furtherspunbonded layer. In certain embodiments, permanently hydrophilicnon-wovens, and in particular, nonwovens with durably hydrophiliccoatings are desirable. Another suitable embodiment comprises aSMMS-structure. In certain embodiments, the non-wovens are porous.

In some embodiments, as shown in FIGS. 7 to 10, the absorbent core ofthe disposable diaper may comprise two or more absorbent structures asdisclosed herein, i.e. absorbent structures which comprise channels,which are combined or superposed. Typically, the absorbent structuresmay be combined such that the thermoplastic adhesive material of thefirst absorbent structure directly contacts the thermoplastic adhesivematerial of the second absorbent structure.

FIGS. 7, 8, 9 and 10 illustrate embodiments wherein a first absorbentstructure 15 comprising an absorbent layer 17 with channels 26 iscombined with a second absorbent structure 15′ comprising an absorbentlayer 17′ with channels 26′. In the shown embodiments, the thermoplasticadhesive material 40 of the first absorbent structure directly contactsthe thermoplastic adhesive material 40′ of the second absorbentstructure. An auxiliary adhesive 60 may be present on the substratelayer of the first and/or second absorbent structure for furtherimmobilization of the absorbent polymer particles (as shown in FIG. 7).In some embodiments, the substrate layer 16′ of the second absorbentstructure 15′ may undulate into the channels 26′ of the second absorbentstructure (as shown in FIGS. 8 and 10) and even into the channels 26 ofthe first absorbent structure 15, where it can be possibly adhered tothe substrate layer 16 of the first absorbent structure (as shown inFIG. 9). Typically, when the substrate layer of one absorbent structureundulates into the channels, the substrate layers of the two absorbentstructures are not coextensive, i.e. one of the substrate layer may bewider or longer to penetrate into the channels 26 and/or 26′.Undulations of the substrate layer into the channels contribute to theintegrity of the channels in dry and wet states.

In embodiments wherein the two or more absorbent structures comprisechannels, it may be that the first and second absorbent structures aremirror images of each other. In these embodiments, the channels 26 ofthe first absorbent structure 15 substantially superpose the channels26′ of the adjacent second absorbent structure 26′, as shown in FIGS. 7,8 and 9. The resulting absorbent core is a laminate of absorbentstructures 17 and 17′ with channels extending substantially through thethickness of the absorbent core (by substantially as used herein it ismeant that the thicknesses of the substrate layers are herebyneglected).

In embodiments wherein the two or more absorbent structures comprisechannels, the first and second absorbent structures may be different. Insome of these embodiments, some of the channels of the two absorbentlayers may superpose (as shown in FIG. 10). In other embodiments, thechannels of one absorbent structure may not superpose the channels ofthe adjacent absorbent structure but are complementary with the channelsof the adjacent structure. By complementary it is meant that thechannels of the second absorbent structure form an extension of thechannels of the first absorbent structure.

In some embodiments, as shown in FIGS. 11 to 13, the absorbent core ofthe disposable diaper may comprise one or more absorbent structures asdisclosed herein, combined with an absorbent structure comprising anabsorbent layer which is free of channels. In these embodiments, theabsorbent structure free of channels comprises a substrate layer and anabsorbent layer as disclosed which is however free of channels. Whenonly one of the absorbent structures comprises said channels, theabsorbent structure with channels may in some embodiments herein becloser to the wearer in use than the absorbent structure(s) withoutchannels.

FIGS. 11, 12 and 13 illustrate embodiments wherein a first absorbentstructure 15 with channels 26 is combined with a second absorbentstructure 15′ free of channels. In the embodiment shown in FIG. 11, thethermoplastic adhesive material 40 of the first absorbent structure 15directly contacts the thermoplastic adhesive material 40′ of the secondabsorbent structure 15′ whereas in FIGS. 12 and 13, the second absorbentstructure 15′ may not comprise any such thermoplastic adhesive material40′ (however, it may be present to immobilize the absorbent layer on thesubstrate layer). An auxiliary adhesive 60 may be present on thesubstrate layer of the first and/or second absorbent structure forfurther immobilization of the absorbent polymer particles 50 (as shownin FIG. 11). In some embodiments, the substrate layer 16 of the firstabsorbent structure 15 may undulate into the channels 26 of the firstabsorbent structure (as shown in FIGS. 12 and 13). The absorbent coremay further comprise an acquisition system 70 that penetrates and fillin the channels (however in some embodiments, the acquisition system maynot fill in the channels). FIG. 13 shows an embodiment wherein theacquisition system 70 comprises a first layer 12 and second layer 13,wherein the second layer fills in the channels.

Method of Making the Absorbent Structure

The absorbent structure having channels herein may be made by any methodcomprising the step of depositing absorbent polymer particles andoptionally cellulose to form an absorbent layer onto a substrate layer,for example by placing first said substrate layer onto raised portionsin the shape and dimensions of said channels to be produced and thendepositing said absorbent polymer particles and optionally cellulosethereon; thereby, the absorbent polymer particles and optionallycellulose may not remain onto said raised portions, but only on theremaining portions of the substrate layer.

The absorbent structure free of channels herein may be made by anymethod comprising the step of depositing absorbent polymer particles andoptionally cellulose as an absorbent layer on a substrate layer.

In some embodiments, the absorbent structure with the substrate layerwith therein two or more channels with substantially no absorbentmaterial is for example obtainable by a method comprising the steps of:

-   a) providing a feeder for feeding said absorbent material (absorbent    polymer particles and optionally cellulose) to a first moving    endless surface, such as a hopper;-   b) providing a transfer means for transferring a substrate layer to    a second moving endless surface;-   c) providing a first moving endless surface, having one or more    absorbent layer-forming reservoirs with a longitudinal dimension and    averaged length, a perpendicular transverse dimension and average    width, and, perpendicular to both, a depth dimension and average    depth, and a void volume for receiving said absorbent material    therein, said reservoir(s) comprising one or more substantially    longitudinally extending raised strips, not having a void volume,    for example each having an average width W of at least 4% or at    least 5% of the average width of the reservoir, and an average    length L of at least 5% and at the most 30% of the average    longitudinal dimension of the reservoir; said reservoir(s) being for    transferring said absorbent material to said second moving endless    surface adjacent and in proximity thereto;-   d) providing a second moving surface, having an outer shell that has    one or more air permeable or partially air permeable receptacles    with for receiving said substrate layer thereon or therein, with a    receiving area and with one or more substantially longitudinally    extending mating strips that may be air impermeable, and having each    an average width of for example W′ of at least 2.5 mm, optionally    from 0.5×W to 1.2×W, an average length of for example L′ being from    about 0.8×L to 1.2×L;    whereby said air-permeable outer shell is connected to one or more    secondary vacuum systems for facilitating retention of the substrate    layer and/or said absorbent material thereon, and whereby, in a    meeting point, said first moving endless surface and said outer    shell are at least partially adjacent to one another and in close    proximity of one another during transfer of said absorbent material    and such that each mating strip is substantially completely adjacent    and in close proximity to a raised strip during transfer of said    absorbent material;-   e) feeding with said feeder an absorbent material to said first    moving endless surface, in at least said reservoir (s) thereof;-   f) optionally, removing any absorbent material on said raised strips    (s);-   g) simultaneously, transferring said substrate layer to said second    moving endless surface, onto or into said receptacle(s);-   h) selectively transferring in said meeting point, said absorbent    material with said first moving endless surface only to said part of    the supporting sheet that is on or in said receiving area of said    receptacle.

Said reservoir(s) may be formed by of a multitude of grooves and/orcavities with a void volume, for receiving said absorbent materialtherein. In some embodiments, the average width W of (each) strip may beat least 6 mm, or for example at least 7 mm, and/or at least at least7%, or for example at least 10% of the average width of the respectivereservoir.

Said grooves and/or cavities may each for example have a maximumdimension in transverse direction which is at least 3 mm, and wherebythe shortest distance between directly neighboring cavities and/orgrooves in substantially transverse dimension, is less than 5 mm.Cavities and/or grooves that are directly adjacent a raised strip mayhave a volume that is more than the volume of one or more, or all oftheir neighboring cavities or grooves, that are not directly adjacentsaid strip or another strip (thus further removed from a strip).

Said first moving endless surface's reservoir may be at least partiallyair permeable and said first moving endless surface may have acylindrical surface with said reservoirs, rotatably moving around astator, comprising a vacuum chamber; said second moving surface's outershell may be cylindrical, rotatably moving around a stator, comprising asecondary vacuum chamber connected to said secondary vacuum system.

The method further comprises the step of i) applying an adhesivematerial to the absorbent structure of step h; and optionally applyingan adhesive material (i.e. a second adhesive material) to said substratelayer, prior to step f, or simultaneously therewith, but in any eventprior to step g).

Step i) 1) may involve straying said first adhesive material in the formof fibers onto said absorbent layer, or part thereof, for examplesubstantially continuously, so it is also present in said channels.

Step i) 2) may involve slot coating or spray-coating the supportingsheet, either continuously, or for example in a pattern corresponding tothe channel pattern. An absorbent structure obtained by said method canthen be combined with an absorbent structure free of channels or withanother absorbent structure made by this method to provide an absorbentcore.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A disposable diaper having a backsheet, atopsheet and an absorbent core disposed therebetween, and an acquisitionlayer disposed between the absorbent core and topsheet, wherein theabsorbent core comprises at least one absorbent structure comprising asubstrate layer and an absorbent layer comprising absorbent material,the absorbent layer comprising: i. a width, N, extending in a transversedimension and a length, M, extending in a longitudinal dimension; ii.front, crotch and back regions arranged sequentially in the longitudinaldimension; and iii. two longitudinal portions delimited by the centrallongitudinal axis of the absorbent structure; wherein the absorbentlayer comprises at least two main channels substantially free of theabsorbent material extending through the thickness of the absorbentlayer and at least present in the crotch region; and at least twosecondary channels substantially free of the absorbent materialextending through the thickness of the absorbent layer, and wherein thesecondary channels are shorter than the main channels; provided thefirst absorbent layer does not comprise channels substantially free ofabsorbent polymer particles extending up to its longitudinal andtransverse edges.
 2. The disposable diaper of claim 1, wherein the mainchannels extend for a length, L, wherein L is up to 90% of the length ofM.
 3. The disposable diaper of claim 1, wherein the secondary channelshave a length, V′, that is up to 45% of M.
 4. The disposable diaper ofclaim 3, wherein V′ is up to 30% of M.
 5. The disposable diaper of claim1 wherein the main channels are straight.
 6. The disposable diaper ofclaim 1 wherein the secondary channels are straight.
 7. The disposablediaper of claim 1 wherein the main channels and/or the secondarychannels have a percentage integrity of at least 20% according to theWet Channel Integrity Test.
 8. The disposable diaper of claim 1, whereintwo of the at least two main channels are mirror images of each otherwith respect to the central longitudinal axis.
 9. The disposable diaperof claim 1, wherein two of the at least two secondary channels aremirror images of each other with respect to the central longitudinalaxis.
 10. The disposable diaper of claim 1, wherein the absorbent layercomprises cellulose.
 11. The disposable diaper of claim 1, wherein eachof the main and/or secondary channels have a width of at least 3 mm. 12.The disposable diaper of claim 1, wherein a majority of at least one ofthe secondary channels is disposed in the front region.
 13. Thedisposable diaper of claim 1, wherein a majority of at least one of thesecondary channel is disposed in the back region.
 14. The disposablediaper of claim 1, wherein the main channels are curvilinear.
 15. Thedisposable diaper of claim 1, wherein at least one secondary channel isoblique or angled.
 16. The disposable diaper of claim 1, wherein atleast one of the main channels is oblique or angled.
 17. The disposablediaper of claim 1, wherein at least one secondary channel extends in thetransverse dimension.
 18. The disposable diaper of claim 1 wherein atleast one main channel extends in the longitudinal dimension.
 19. Thedisposable diaper of claim 1 wherein at least one second channel extendsin the longitudinal dimension.
 20. The disposable diaper of claim 1further comprising a second absorbent structure having absorbentmaterial disposed on a second substrate layer, wherein the substratelayer and the second substrate layer are images of each other and arecombined such that the channels of the second absorbent layer superposethe channels of the absorbent layer to form channels through thethickness of the laminate.
 21. A disposable diaper having a backsheet, atopsheet and an absorbent core disposed therebetween, wherein theabsorbent core comprises at least one absorbent structure comprising asubstrate layer and an absorbent layer comprising absorbent material,the absorbent layer comprising: i. a width, N, extending in a transversedimension and a length, M, extending in a longitudinal dimension; ii.front, crotch and back regions arranged sequentially in the longitudinaldimension; and wherein the absorbent layer comprises one or more mainchannels substantially free of the absorbent material extending throughthe thickness of the absorbent layer; one or more secondary channelssubstantially free of the absorbent material extending through thethickness of the absorbent layer; wherein the at least two main channelsare separated by a first minimum transverse spacing, and wherein the atleast two secondary channels are separated by a second minimumtransverse spacing, and wherein the first minimum transverse spacing isdifferent than the second minimum transverse spacing; provided theabsorbent layer does not comprise channels substantially free ofabsorbent polymer particles extending up to its longitudinal andtransverse edges.
 22. The disposable diaper of claim 21 wherein one ormore main channels are straight and/or wherein the one or more secondarychannels are straight.
 23. The disposable diaper of claim 21 furthercomprising a second absorbent structure having absorbent materialdisposed on a second substrate layer, wherein the substrate layer andthe second substrate layer are images of each other and are combinedsuch that the channels of the second absorbent layer superpose thechannels of the absorbent layer to form channels through the thicknessof the laminate.